Hydrogen Bridges Research Articles

Ring current and anisotropy effects on OH chemical shifts in resonance-assisted intramolecular H-bonds

Ring current effects on resonance-assisted and intramolecularly bridged hydrogen bond protons for 10-hydroxybenzo[h]quinoline 1 and a number of related compounds were calculated and the through-space NMR shieldings (TSNMRS) obtained hereby visualized as iso-chemical-shielding surfaces (ICSS) of various size and direction. These calculations revealed that this through-space effect is comparably large (up to 2 ppm) dependent on the position of the intramolecularly bridged OH proton, and therefore, contribute considerably to the chemical shift of the latter making it questionable to use δ(OH)/ppm in the estimation of intramolecular hydrogen bond strength without taking this into account. Furthermore, the anisotropy effects of additional groups on the aromatic moiety (e.g. the carbonyl group in salicylaldehyde or in o-hydroxyacetophenone of ca. 0.6 ppm deshielding) should also be considered. These through-space effects need to be taken into account when using OH chemical shifts to estimate hydrogen bond strength.

Bottleable Neutral Analogues of [B2 H5 ]- as Versatile and Strongly Binding η2 Donor Ligands.

Herein we report the discovery that two bottleable, neutral, base-stabilized diborane(5) compounds are able to bind strongly to a number of copper(I) complexes exclusively through their B-B bond. The resulting complexes represent the first known complexes containing unsupported, neutral σB-B diborane ligands. Single-crystal X-ray analyses of these complexes show that the X-Cu moiety (X=Cl, OTf, C6 F5 ) lies opposite the bridging hydrogen atom of the diborane and is near perpendicular to the B-B bond, interacting almost equally with both boron atoms and causing a B-B bond elongation. DFT studies show that σ donation from and π backdonation to the pseudo-π-like B-B bond account for their formation. Astoundingly, these copper σB-B complexes are inert to ligand exchange with pyridine under either heating or photoirradiation.

Structure, properties and interactions in ionomer/lignin blends

Blends were prepared from lignin and ionomers, i.e. ethylene-methacrylic acid copolymers partially neutralized with inorganic salts for the first time in order to check the possible effect of ionic bonds on the structure and properties of the blends. A low density polyethylene and an ethylene-acrylic acid copolymer without any neutralization were used as references. The lignin content of the blends varied between 0 and 60 vol%. The components were homogenized in an internal mixer and the blends were characterized by various methods including dynamic mechanical analysis, differential scanning calorimetry and tensile testing. The size of dispersed lignin particles was determined from scanning electron micrographs, and component interactions were estimated quantitatively. The properties of ionomer/lignin blends indicated the development of strong interactions between the components. The simultaneous action of hydrogen bonds of non-neutralized methacrylic acid moieties and ionic bonds resulted in the formation of small, dispersed lignin particles of the size of several tenth of a micron. Surprisingly, hydrogen bridges improve interactions and compatibility more than ionic bonds. Contrary to most blends prepared from other polymers, ionomer/lignin blends can be produced with a reasonable combination of properties at moderate lignin contents.

X-ray Diffraction and Density Functional Theory Provide Insight into Vanadate Binding to Homohexameric Bromoperoxidase II and the Mechanism of Bromide Oxidation.

X-ray diffraction of native bromoperoxidase II (EC 1.11.1.18) from the brown alga Ascophyllum nodosum reveals at a resolution of 2.26 Å details of orthovanadate binding and homohexameric protein organization. Three dimers interwoven in contact regions and tightened by hydrogen-bond-clamped guanidinium stacks along with regularly aligned water molecules form the basic structure of the enyzme. Intra- and intermolecular disulfide bridges further stabilize the enzyme preventing altogether the protein from denaturing up to a temperature of 90 °C, as evident from dynamic light scattering and the on-gel ortho-dianisidine assay. Every monomer binds one equivalent of orthovanadate in a cavity formed from side chains of three histidines, two arginines, one lysine, serine, and tryptophan. Protein binding occurs primarily through hydrogen bridges and superimposed by Coulomb attraction according to thermochemical model on density functional level of theory (B3LYP/6-311++G**). The strongest attractor is the arginine side chain mimic N-methylguanidinium, enhancing in positive cooperative manner hydrogen bridges toward weaker acceptors, such as residues from lysine and serine. Activating hydrogen peroxide occurs in the thermochemical model by side-on binding in orthovanadium peroxoic acid, oxidizing bromide with virtually no activation energy to hydrogen bonded hypobromous acid.

Theoretical Study of the Structure and Stability of Stepwise Hydrogenated Aluminum Clusters Al44H n (n = 1−24)

The energies and structural and spectroscopic characteristics of a series of model stepwise hydrogenated aluminum clusters Al44H n (n = 1−24) obtained by successive introduction of hydrogen atoms into various surface positions of the Al44 cluster have been calculated by the density functional theory method (B3LYP). According to these calculations, the [Al39] surface layer of the cage retains a closed “nested doll” shape with a pentaatomic inner core [Al5]. With increasing n, both the surface layer and the core tend to experience increasing asymmetric distortions. The surface is corrugated and undergoes significant axial and equatorial extensions and contractions, some of the Al−H two-center terminal bonds are transformed into threecenter hydrogen bridges, and some Al atoms are displaced from the surface layer to the outer sphere and are bound to the surface through hydrogen bridges. The inner core [Al5] at n = 24 loses its bipyramidal shape and shifts to the surface layer so that one or two of its atoms are “built-in” into the concave regions of the surface layer. The calculated average energies of Al−H bonds are within the range ~55.5 ± 2.5 kcal/mol. The averaged energies of the Al44H n → Al44Hn–2 + Н2 dissociation reactions with elimination of a hydrogen molecule are on the order of a few kilocalories per mole and are evidence of small exothermicity (or isothermicity) of these reactions. For the Al44H, Al44H2, and Al44H6 clusters as an example, the relative stabilities of isomers with terminal Al−H bonds in various nonequivalent positions of the [Al39] surface layer are compared.

Dynamic Mechanism of a Fluorinated Oxime Reactivator Unbinding from AChE Gorge in Polarizable Water.

A well-tempered metadynamics simulation is performed to study the unbinding process of a fluorinated oxime (FHI-6) drug from the active-site gorge of acetylcholinesterase enzyme in a polarizable water medium. Cation-π interactions and water bridge and hydrogen bridge formations between the protein and the drug molecule are found to strongly influence the unbinding process, forming basins and barriers along the gorge pathway. Distinct unbinding pathways are found when FHI-6 was compared with its recently reported nonfluorinated analogue, HI-6. For example, because of permanent positive charges on both the pyridinium rings of HI-6, it exhibits the minimum in the potential of mean force of the unbinding process in the gorge mouth (where the peripheral anion site, PAS, of the enzyme is located), which is largely caused by cation-π interactions. However, the same interaction, both in the catalytic active-site (CAS) and PAS regions, is found to be greatly enhanced in its lipophilic fluorinated analogue, FHI-6, causing a deep potential energy minimum in the bound state. This may render FHI-6 to be held more firmly in the CAS region of the gorge, as is also evidenced from the microkinetics of unbinding transitions, measured through a combination of metadynamics and hyperdynamics simulations.

From Noncovalent Chalcogen-Chalcogen Interactions to Supramolecular Aggregates: Experiments and Calculations.

This review considers noncovalent bonds between divalent chalcogen centers. In the first part we present X-ray data taken from the solid state structures of dimethyl- and diphenyl-dichalcogenides as well as oligoalkynes kept by alkyl-sulfur, -selenium, and -tellurium groups. Furthermore, we analyzed the solid state structures of medium sized (12-24 ring size) selenium coronands and medium to large rings with alkyne and alkene units between two chalcogen centers. The crystal structures of the cyclic structures revealed columnar stacks with close contacts between neighboring rings via noncovalent interactions between the chalcogen centers. To get larger space within the cavities, rings with diyne units between the chalcogen centers were used. These molecules showed channel-like structures in the solid state. The flexibility of the rings permits inclusion of guest molecules such as five-membered heterocycles and aromatic six-membered rings. In the second part we discuss the results of quantum chemical calculations. To treat properly the noncovalent bonding between chalcogens, we use diffuse augmented split valence basis sets in combination with electron correlation methods. Our model substances were 16 dimers consisting of two Me-X-Me (X = O, S, Se, Te) pairs and dimers of Me-X-Me/Me-X-CN (X = O, S, Se, Te) pairs. The calculations show the anticipated increase of the interaction energy from (Me-O-Me)2 (-2.15 kcal/mol) to (Me-O-Me/Me-Te-CN) (-6.59 kcal/mol). An analysis by the NBO method reveals that in the case of the chalcogen centers O and S the hydrogen bridges between the molecules dominate. However, in the case of Se and Te the major bonding between the pairs originates from dispersion forces between the chalcogen centers. It varies between -1.7 and -4.0 kcal/mol.

Electron Precise Group 5 Dimetallaheteroboranes [{CpV(μ-EPh)}2{μ-η2:η2-BH3E}] and [{CpNb(μ-EPh)}2{μ-η2:η2-B2H4E}] (E = S or Se).

Synthesis and structural elucidation of various electron precise group 5 dimetallaheteroboranes have been described. Room temperature reaction of [Cp2VCl2] with Li[BH3(EPh)], generated from the treatment of LiBH4·THF and Ph2E2 (E = S or Se), for 1 h in toluene, followed by thermolysis, led to the formation of bimetallic complexes [{CpV(μ-EPh)}2{μ-η2:η2-BH3E}], 1 and 2 (1: E = S and 2: E = Se), and [{CpV(μ-SePh)}2{μ-η2:η2-BH(OC4H8)Se}], 3. One of the striking features of these compounds is that they represent a rare class of distorted tetrahedral clusters having bridging hydrogens. Evaluating the skeletal electron pairs and bonding types, compounds 1, 2, and 3 may be considered as isoelectronic with our earlier reported [(CpV)2(B2H6)2]. In an attempt to synthesize the Nb analogues of 1-3, room temperature reactions of [CpNbCl4] and Li[BH3(EPh)] (E = S or Se) were carried out that afforded compounds [{CpNb(μ-EPh)}2{μ-η2:η2-B2H4E}], 4 and 5 (4: E = S and 5: E = Se). The solid-state X-ray structures of both 4 and 5 exemplify electronically saturated [M2B3] systems, and their geometries are analogous to that of [(Cp*MoCl)2B3H7]. For the extension of this work, reaction of [Cp*TaCl4] (Cp* = η5-C5Me5) with Li[BH3(SePh)] was carried out that yielded a tantalaselenaborane cluster [(Cp*Ta)2(μ-Se)B3H6Se(C6H5)] (6). All the new compounds have been characterized using 1H, 11B{1H}, 13C{1H} NMR, UV-vis absorption, and IR spectroscopy, mass spectrometry, and X-ray diffraction studies.

Switching the Proton Conduction in Nanoporous, Crystalline Materials by Light.

Proton conducting nanoporous materials attract substantial attention with respect to applications in fuel cells, supercapacitors, chemical sensors, and information processing devices inspired by biological systems. Here, a crystalline, nanoporous material which offers dynamic remote-control over the proton conduction is presented. This is realized by using surface-mounted metal-organic frameworks (SURMOFs) with azobenzene side groups that can undergo light-induced reversible isomerization between the stable trans and cis states. The trans-cis photoisomerization results in the modulation of the interaction between MOF and guest molecules, 1,4-butanediol and 1,2,3-triazole; enabling the switching between the states with significantly increased (trans) and reduced (cis) conductivity. Quantum chemical calculations show that the trans-to-cis isomerization results in the formation of stronger hydrogen bridges of the guest molecules with the azo groups, causing stronger bonding of the guest molecules and, as a result, smaller proton conductivity. It is foreseen that photoswitchable proton-conducting materials may find its application in advanced, remote-controllable chemical sensors, and a variety of devices based on the conductivity of protons or other charged molecules, which can be interfaced with biological systems.

Structural diversity in the alkaline earth metal compounds of tetra and pentacyanocyclopentadienide

The reaction of the alkaline earth dihalides MCl2·nH2O (M = Mg, Ca, Sr, Ba) with the silver salts of cyanocyclopentadienides [C5(CN)4X]- (X = H, CN) yields the corresponding alkaline earth biscyclopentadienides. The pentacyanocyclopentadienides of Mg and Ca and the tetracyanocyclopentadienides of Ca, Sr and Ba were studied by X-ray diffraction. The Mg compound 1a' shows only coordination by water molecules, but numerous hydrogen bridges between coordinated water molecules and pentacyanocyclopentadienide anions and further guest water molecules create a three-dimensional network. The structure of the calcium pentacyanocyclopentadienide 1b shows two inequivalent anions, one uncoordinated and one coordinating via three nitrile groups to three different metal ions. Ca2+ and [C5(CN)5]- ions together form a rhombohedral grid structure, in which the voids are filled by the uncoordinated [C5(CN)5]- ion and guest water molecules, all taking part in a hydrogen bond network too. The isostructural Ca and Sr tetracyanocyclopentadienides exhibit eightfold coordinated metal ions, in which both [C5(CN)4H]- anions coordinate to the metals by one cyano group each, and each anion bridging two metal ions. Thus, one-dimensional ribbons of {Ca[C5(CN)4H]4/2}x are formed, which are interconnected via hydrogen bridges from and to coordinated water molecules to build a three-dimensional network. The barium tetracyanocyclopentadienide contains a ninefold coordinated metal with the anion using three of its nitrile functions for coordination to three different metals. A complicated network is formed by four interpenetrating {Ba[C5(CN)4H]2} helices that are interconnected via the remaining third nitrile function, while the fourth nitrile group always remains uncoordinated. Although all coordinated water molecules are involved in hydrogen bridges, these are not contributing to the formation of the network.

A molecular roundabout: triple cyclically arranged hydrogen bonds in light of experiment and theory

This paper dwells on the synthesis and diverse studies of cyclically arranged hydrogen bridges in tris-hydroxy aryl Schiff bases. Experimental (IINS, IR, Raman and X-ray) and theoretical (CPMD, DFTP and DFT) studies of tris-hydroxy aryl Schiff bases have been performed in the solid state.

Comparison of Degrees of Potential-Energy-Surface Anharmonicity for Complexes and Clusters with Hydrogen Bonds

Previously calculated multidimensional potential-energy surfaces of the MeOH monomer and dimer, water dimer, malonaldehyde, formic acid dimer, free pyridine-N-oxide/trichloroacetic acid complex, and protonated water dimer were analyzed. The corresponding harmonic potential-energy surfaces near the global minima were constructed for series of clusters and complexes with hydrogen bonds of different strengths based on the behavior of the calculated multidimensional potential-energy surfaces. This enabled the introduction of an obvious anharmonicity parameter for the calculated potential-energy surfaces. The anharmonicity parameter was analyzed as functions of the size of the analyzed area near the energy minimum, the number of points over which energies were compared, and the dimensionality of the solved vibrational problem. Anharmonicity parameters for potential-energy surfaces in complexes with strong, medium, and weak H-bonds were calculated under identical conditions. The obtained anharmonicity parameters were compared with the corresponding diagonal anharmonicity constants for stretching vibrations of the bridging protons and the lengths of the hydrogen bridges.

Model molecules to classify CHO hydrogen-bonds.

We developed a set of conformationally locked molecules each of which makes a single CHO H-bond/short contact and has different electron density at the acceptor oxygen atom. The downfield shift of the 1H NMR signals due to the hydrogen involved in the CHO H-bond varied from 0.93-1.6 ppm, and the magnitude of Δδ is in correlation with the hybridization state of the acceptor oxygen and with the CHO H-bond strengths quantified using a computational method.

The Intramolecular Hydrogen Bond N-H···S in 2,2'-Diaminodiphenyl Disulfide: Experimental and Computational Thermochemistry.

The intramolecular hydrogen bond of the N-H···S type has been investigated sparingly by thermochemical and computational methods. In order to study this interaction, the standard molar enthalpies of formation in gaseous phase of diphenyl disulfide, 2,2'-diaminodiphenyl disulfide and 4,4'-diaminodiphenyl disulfide at T = 298.15 K were determined by experimental thermochemical methods and computational calculations. The experimental enthalpies of formation in gas-phase were obtained from enthalpies of formation in crystalline phase and enthalpies of sublimation. Enthalpies of formation in crystalline phase were obtained using rotatory bomb combustion calorimetry. By thermogravimetry, enthalpies of vaporization were obtained, and by combining them with enthalpies of fusion, the enthalpies of sublimation were calculated. The Gaussian-4 procedure and the atomization method were applied to obtain enthalpies of formation in gas-phase of the compounds under study. Theoretical and experimental values are in good agreement. Through natural bond orbital (NBO) analysis and a topological analysis of the electronic density, the intramolecular hydrogen bridge (N-H···S) in the 2,2'-diaminodiphenyl disulfide was confirmed. Finally, an enthalpic difference of 11.8 kJ·mol-1 between the 2,2'-diaminodiphenyl disulfide and 4,4'-diaminodiphenyl disulfide was found, which is attributed to the intramolecular N-H···S interaction.

Optical properties of polyimides films treated by nanosecond pulsed electrical discharges in water

Fluorinated polyimide films containing cobalt chloride based on hexafluoroisopropylidenediphthalic dianhydride and 4,4′-diamino-3,3′-dimethyl diphenylmethane were treated by nanosecond pulsed electrical discharges generated in distilled water. The polyimide films have been characterized by Fourier transform infrared (FTIR) spectra and contact angle measurements, optical transmission spectroscopy, and fluorescence spectroscopy. Significant changes in some intrinsic fluorescence features, such as the intensity and position of the emission peak, have been observed during exposure to water plasma. These effects have been considered to correlate with the development of specific chemical interactions between the liquid and the macromolecules, including the formation of hydrogen bridges. A slight increase in surface hydrophobicity was observed after plasma treatment. FTIR spectra showed a decrease in the intensity of the absorption band and an opening of the imide ring, depending on the treatment time.

H-bonded supramolecular synthon induced magnetic superexchange phenomenon results weak ferromagnetic and strong antiferromagnetic interactions in two new copper-orotate coordination network

Hydrothermal self-assembly of orotic acid (C5H4N2O4OrH3) with metal salt Cu(Ac)2·H2O yielded a new OrH based hydrogen bonded coordination network of formula [Cu(OrH)(2NH3)(H2O)]·H2O (1) and [Cu(OrH) (2NH3)]2 (2). Single crystal X–ray study on 1 confirms that +2 charges on the metal ions (Cu2+) are balanced by OrH anion. N–H⋯O and O–H⋯O hydrogen bonding synthons are the only artifact for the resulting hydrogen bonded copper-OrH architecture. Temperature dependent measurements of magnetic susceptibility reveals the occurrence of competitive exchange interactions with a net ferromagnetic character in 1 (J = +0.48 cm−1) and strong antiferromagnetic interaction in 2 (J = −4.93 cm−1). Magnetic superexchange interaction transmitted through equatorial–axial hydrogen bridge system promotes weak ferromagnetic interactions in 1 while in 2 it is in basal-basal position, in which two dx2-y2orbitals is involved in exchange mechanism reveals the coexistence of two antiferromagnetic exchange pathways, intramolecular much stronger than intermolecular. The natural bond orbital (NBO) analysis applied separately to α and β spin density matrices clearly shows two important magnetic superexchange pathway with shorter Cu⋯Cu contact 5.542(4) Å and 4.845(4) Å or 5.755(1) Å in (1) and inter dimer 6.665(1) Å and 4.6744(9) Å for (2).

Phase transition and proton ordering at 50 K in 3-(pyridin-4-yl)pentane-2,4-dione

Single-crystal neutron diffraction experiments at 100 and 2.5 K have been performed to determine the structure of 3-(pyridin-4-yl)pentane-2,4-dione (HacacPy) with respect to its protonation pattern and to monitor a low-temperature phase transition. Solid HacacPy exists as the enol tautomer with a short intramolecular hydrogen bond. At 100 K, its donor···acceptor distance is 2.450 (8) Å and the compound adopts space group C2/c, with the N and para-C atoms of the pyridyl ring and the central C of the acetylacetone substituent on the twofold crystallographic axis. As a consequence of the axial symmetry, the bridging hydrogen is disordered over two symmetrically equivalent positions, and the carbon–oxygen bond distances adopt intermediate values between single and double bonds. Upon cooling, a structural phase transition to the t 2 subgroup P\bar 1 occurs; the resulting twins show an ordered acetylacetone moiety. The phase transition is fully reversible but associated with an appreciable hysteresis in the large single crystal under study: transition to the low-temperature phase requires several hours at 2.5 K and heating to 80 K is required to revert the transformation. No significant hysteresis is observed in a powder sample, in agreement with the second-order nature of the phase transition.

Atomic hydrogen bridge fueling NGC 4418 with gas from VV 655

The galaxy NGC 4418 harbours a compact ($<20$ pc) core with a very high bolometric luminosity ($\sim10^{11}$L$_\odot$). As most of the galaxy's energy output comes from this small region, it is of interest to determine what fuels this intense activity. An interaction with VV 655 has been proposed, where gas aquired by NGC 4418 could trigger intense star formation and/or black hole accretion in the centre. We aim to constrain the interaction hypothesis by studying neutral hydrogen structures around the two galaxies. We present observations at 1.4 GHz with the Very Large Array of radio continuum as well as emission and absorption from atomic hydrogen. Gaussian distributions are fitted to observed HI emission and absorption spectra. An atomic HI bridge is seen in emission, connecting NGC 4418 to VV 655. While NGC 4418 is bright in continuum emission and seen in HI absorption, VV 655 is barely detected in the continuum but show bright HI emission (M$_\mathrm{HI}\sim10^9$ M$_\odot$). We estimate SFRs from 1.4 GHz of 3.2 M$_\odot$ yr$^{-1}$ and 0.13 M$_\odot$ yr$^{-1}$ for NGC 4418 and VV 655 respectively. Systemic HI velocities of 2202$\pm$20 km s$^{-1}$ (emission) and 2105.4$\pm$10 km s$^{-1}$ (absorption) are measured for VV 655 and NGC 4418 respectively. Redshifted HI absorption is seen towards NGC 4418, suggesting gas infall. Blueshifted HI-emission is seen north-west of NGC 4418, which we interpret as a continuation of the outflow previously discussed by Sakamoto et al. (2013). The morphology and velocity structure seen in HI is consistent with an interaction scenario, where gas was transferred from VV 655 to NGC 4418, and may fuel the activity in the centre.

Tetraorganopnictonium and Alkali Metal Salts of Pyridine‐2,6‐di‐tetrazolate

Alkali metal (Na, K) and tetraorganopnictonium (AsPh4, PPh4) salts were prepared from 2,6‐bis(1H‐tetrazol‐5‐yl)pyridine (H2pydtz) and characterized by multinuclear NMR, IR, and UV/Vis absorption spectroscopy. Single crystal XRD of (AsPh4)2(pydtz)·5H2O reveals isolated pydtz2– dianions sandwiched between two AsPh4+ cations and an interesting hydrogen bridging network comprising the five co‐crystallized water molecules and the three pydtz N atoms. (PPh4)2(pydtz)·5H2O is isostructural to (AsPh4)2(pydtz)·5H2O as revealed from powder XRD measurements and corresponding Rietveld fits. The crystal structure of the mixed salt Na3(PPh4)(pydtz)2·12H2O reveals π‐stacking interaction of the pydtz2–, a polymeric chain of water molecules and Na+ cations in an extended hydrogen bonding and Na+‐coordinating network. PPh4+ cations interact solely through their positive charge. The alkali metal salts were soluble in water, alcohols, and DMF, whereas the pnictonium salts were additionally soluble in less polar solvents such as acetone, DMSO, CH2Cl2, or THF.

Preparation of Co3O4 Nanoparticles via Thermal Decomposition of Three New Supramolecular Structures of Co(II) and (III) Containing 4′-Hydroxy-2,2′:6′,2′′-Terpyridine: Crystal Structures and Thermal Analysis Studies

Three cobalt(II) and (III) complexes based on the 4′-hydroxy-2,2′:6′,2"-terpyridine (tpyOH) have been synthesized and structurally characterized by X-ray crystallography. The reaction of tpyOH with CoCl2·6H2O in a mixture of methanol/CH2Cl2 resulted in the formation of the new complex [CoIICl2(tpyOH)] (1). On the other hand, the reaction of CoCl2·6H2O with tpyOH in a 2:1 or 1:1 mol ratio in methanol under reflux condition affords the new complexes [CoIII(tpyOH)(tpyO)][CoIICl4]·H2O (2) and [CoIIICl2(H2O)(tpyO)]·H2O (3), respectively. Moreover, the treatment of a methanolic solution of CoCl2·6H2O with tpyOH in a branched tube at 60 °C resulted in the formation of three quality crystals of the complexes 1 and 2 as the major products as well as the complex 3 as a minor product. The crystal structure of [CoCl2(tpyOH)] (1) reveals that the cobalt(II) is penta-coordinated by two Cl− and three nitrogen atoms of tpyOH in a distorted square pyramidal geometry. The complex [CoIII(tpyOH)(tpyO)][CoIICl4]·H2O (2) is described as a highly distorted octahedral geometry [CoN6] while the X-ray crystal structure of the complex [CoIIICl2(H2O)(tpyO)]·H2O (3) shows that cobalt(III) is hexa-coordinated in a slightly distorted octahedral geometry CoCl2N3O. Several strong noncovalent interactions are present in the crystal structure of 1–3. The hydrogen bonding in 1 involves the OH⋯Cl bridges while there is a hydrogen bonding between tpyO and tpyOH of the next molecule in 2 and hydrogen bridges and π–π interactions for 3, connecting molecules and ions in the crystalline 1–3 to form supramolecular networks. The thermal stabilities of the cobalt complexes reveal that the loss of free terpyridine ligand could not be observed in low temperatures. The hexagonal and spherical Co3O4 nanoparticles (NPCs) were prepared by direct calcination of complexes 1–3 at 600 °C in air. The nanostructures of the products were characterized by IR, powder X-ray diffraction, field emission scanning electron microscopy and energy-dispersive X-ray spectroscopy which show the purity of the resulting Co3O4 NPCs. The average particle size using Scherrer’s equation is calculated to be about 32–35 nm.